Tenneswede gave you an excellent selection, I was concerned about you as so many beginners getting overwhelmed by the entomology. I carry a couple vials with me on stream and collect "bugs" that fish seem to like and try to tie flies that copy them. Having taught Biology in HS and College, I can tell you that the people more than trout care about the latin names. They just know that the yellow mayfly with some orange *(a Sulfur) and the small yellow stoneflies (Yellow Sallies) taste good.
Learn to identify the few basic flies of mayflies, stoneflies and caddis found where you fish, their LIFE CYCLES and then ENJOY FISHING. Call LRO and ask them to suggest a good basic book or two. As you learn the basics you can expand from there and get as technical as you wish.